The present invention relates to brakes, and more particularly to a brake apparatus that provides a remote indication of the need to replace friction pads.
Brakes of the type used on automobiles, aircraft and other vehicles employ high friction brake pads attached by rivets to shoes which are connected to the vehicle frame so they cannot rotate. When the brake is applied, the shoe is moved to engage a smooth metal member in the form of a disk or drum that rotates with a wheel of the vehicle. The friction between the stationary pad and the rotating member provides the braking force. The friction surface of the pad is gradually worn away until the pad has been consumed and must be replaced.
If expensive repairs are to be avoided, it is imperative that the pads be replaced before they are worn to the point at which the rivets contact and score the rotatable member. The life expectancy of a pad may be predicted, within broad limits, based on the wear resistance of the material of which it is made and the working thickness between its original friction surface and the heads of the rivets. Nevertheless, variations in individual driving habits make accurate prediction of replacement intervals impossible. Most vehicles, therefore, require frequent visual inspection of pads, which is a time-consuming and inconvenient process, to guard against brake damage. Failure to inspect brake pads with sufficient frequency is not unusual.
It is, therefore, highly desirable to provide a remote indicator responsive to the need to replace brake pads, preferably providing an instrument panel display, to eliminate the need for brake pad inspection. Various arrangements have been proposed to this end. One such arrangement, described in U.S. Pat. No. 3,869,695, to Kita, utilizes an electrical wire embedded in the pad and protruding above the level of the rivets so that it is severed by the action of a disk or rotor before the rotor contacts the rivets. An electronic circuit is responsive to the severance of this wire to produce an indication that the pad should be replaced.
An objective of the present invention is to provide an improved remote brake-pad-wear indicator of simple construction that does not require the expense and weight of copper wire extending from each brake to the location where the indication is to be displayed. Another objective of the invention is to provide a remote wear indicator that is highly effective and reliable despite any misalignment between the friction pad and the rotatable member by which it is engaged.